The present invention relates to a technique of connecting nerve cells in a living body to each other.
The nerve growth mechanism has not been made clear. However, there have been reported some investigation results on external and internal factors. As an example of the external factor, the NGF (nerve growth factor) for sensory nerves contained in a mouse tumor is known.
This will be explained with reference to FIGS. 8 (a)-8(c). If a target cell 102 exists in the vicinity of a neuron 101 of a sympathetic ganglion, NGFs are secreted from the target cell 102 (FIG. 8(a)). Then, an axis cylinder 103 extends from the neuron 101 (FIG. 8(b)) and finally reaches the target cell 102, so that the neuron 101 is connected to the target cell 102 (FIG. 8(c)).
The mechanism in which a lateral branch germinates and extends from an axis cylinder of a nerve cell to create synapse connection of nerves is explained, for example, as illustrated in FIGS. 9(a) and 9(b). Assume that nerve cells A.sub.1 -D.sub.1 are connected to muscle fibers A.sub.2 -D.sub.2 respectively as shown in FIG. 9(a). If the nerve cells C.sub.1 and D.sub.1 are cut off along broken line 104 for some reason, the muscle fibers C.sub.2 and D.sub.2 can not react to stimulation any more. After a lapse of time, however, lateral branches 106 germinate from axis cylinders 105 of the nerve cells C.sub.1 and D.sub.1, and gradually extend. The branches 106 are finally connected to other nerve cells in about two weeks. In FIG. 9(a), reference numeral 107 and 108 represent a Schwann cell and a nerve ending. In FIG. 9(b), numeral 109 denotes a degenerated cell.
However, two weeks, which nerve cells take to connect to each other on a natural mechanism, are too long and cause inconveniences for the purposes of experiments or medical treatments. Consequently, it is desired to realize faster connection of nerve cells.